The present invention relates to vacuum circuit interrupters which are used to interrupt electric currents in electric power transmission and distribution systems. A conventional interrupter includes a generally cylindrical insulating envelope portion with a pair of contacts hermetically sealed through end plates sealed to the insulating envelope, with the device being evacuated. One of the contacts is movable along the device axis to make and break contact with the fixed contact from a mating closed contact, current carrying position to an open contact, spaced apart circuit interrupting position.
The conventional structure for permitting contact movement is a generally cylindrical bellows which is hermetically sealed at one end to an end plate, and at the other end to the contact which extends slidably through a guide bushing in the end plate.
It has been the practice to fasten the guide bushing to the end plate by the use of an adhesive, by welding or by studs and bolts located in the end plate and guide bushing. The use of adhesive has been found to be unreliable and welding requires a significant degree of device handling which can result in damage to the vacuum interrupter. Bolting the guide bushing to the end plate is an adequate technique but, the requirement of studs on either the bushing or end plate is an undesirable expense. Alternatively, it has been known to use flat head screws fastened into holes tapped in the end plate to secure the guide bushing. This method is also unnecessarily expensive.
It is an object of this invention to provide a guide bushing retaining means which is reliable, inexpensive and simplified in its installation.